New spider species highlights global threats to spider populations

Whilst not everyone's favourite group of animals, spiders play a variety of important ecosystem roles. I personally am a big fan of spiders, with their diversity of hunting techniques, stunning colours, and just fascinating behaviours. Recently, a new species of trapdoor spider has been discovered in Australia. Finding a new species is always exciting but it's existence and rarity highlight some issues threatening our spiders.

​New Species
We'll kick off with the positive - the newly discovered species. Researchers involved in Queensland Museum's project DIG, which aims to understand more about the State's biodiversity, found a new, rare, giant trapdoor spider they have named Euoplos dignitas. Eulopos is a group of spiders, known as the golden trapdoor spiders, and 'dignitas' is a Latin epithet that means dignity or greatness.

The spider was discovered in the band of acacia-wooded grassland that runs between the tropical rainforest of the coast and the semi-arid interior of Queensland, known as the Brigalow belt. Specifically, within the black soil around Eidsvold and Monto, west of Bundaberg.

E. dignitas is a large, nocturnal, plug door-building trapdoor spider that displays a strong degree of sexual dimorphism. The males are a beautiful honey-red, whilst the females are darker and stockier, because they spend their entire lives underground, whereas the males leave their burrows to go looking for a female. Despite their large size, like the other Australian trapdoor spiders, their venom is not dangerous to humans. They can live up to 20 years and take between 5-8 years to reach maturity and start breeding.

Whilst this is exciting news, the rarity of this species highlights issues facing spider populations around the world.

​Land use and spider populations
The researchers who discovered E. dignitis are concerned about the future of the species as it doesn't appear to be doing well in the wild. The International Union for Conservation of Nature's Red List (IUCN Red List) classify it as an endangered species.

​Trapdoor spiders are suited to woodlands, however many of these habitats have been lost due to clearing for agriculture. Unlike flying insects, they do not have the ability to quickly relocate to a new, suitable area, and the long time until maturity reduces their ability to reproduce quickly. These factors put E. dignitis at particular risk, but many spiders face these issues.

It's no secret that across the world a variety of habitats are being lost due to deforestation, and other forms of habitat clearing, so the land can be used for agriculture and human development. We often focus on how this impacts the large, charismatic animals and overlook the impacts on the invertebrates. As mentioned above, spiders can be particularly vulnerable.

Often the cleared forests are replaced with large monocultural plantations. Despite giving the appearance of a healthy habitat with lots of vegetation, they lack diversity and therefore do not support a rich ecosystem. Spiders can actually act as an indicator of a healthy habitat, where there are lots of spiders, there is likely to be a lot of insects for the spiders to eat. A healthy ecosystem is required to support that diversity.

This drops dramatically when habitats are changed. For example, researchers used the number of spider species to monitor the health of the Atlantic Forests (a stretch of woodland in South America) as it was cleared for pine farms. As the forest began to disappear, a third of the 126 spider species that originally inhabited the forest were also lost. Even a decade letter, the spider population had not recovered and the species inhabiting the pine plantation differed from the original native population.

This is a prime example of how land use change can drastically alter spider, and other invertebrate, populations. Given their importance in supporting healthy ecosystems, this has wide-reaching consequences.

Conclusion
It is certainly exciting that a new spider species has been discovered in Australia, especially a stunning trapdoor species. However, its rarity and vulnerability to habitat change reflects the struggles of the global spider populations. We continue to alter habitats and replace healthy, mature, and diverse ones with young and simple ones, lacking diversity. This impacts the entire ecosystems, including the invertebrates.

More information
The original publication (although it is behind a paywall) - Rix, M.G., Wilson, J.D. and Oliver, P.M., 2023. A new species of Endangered giant trapdoor spider (Mygalomorphae: Idiopidae: Euoplos) from the Brigalow Belt of inland Queensland, Australia. The Journal of Arachnology, 51(1), pp.27-36.

News article in The Independent containing a photo of the spider.

Oversimplified - Deforestation cuts down spider species - A nice summary of the original paper which is behind a paywall - ​Munévar, A., Cardoso, P. and Zurita, G.A., 2022. From forest to forestry: Reassembly of spider communities after native forest replacement by pine monocultures. Ecological Entomology, 47(3), pp.400-410.